Which adjectives can describe verbs?

Certain nouns can also be verbs, i.e. run or play. Some adjectives can be applied to both forms of such a word, by switching the positioning:

• Run fast
• Fast run
• Play clean
• Clean play

But this isn't always possible -- Play seriously vs serious play -- the adjective changes its form. What is the name for this? I'm looking for a list of adjectives that go after a verb.

P.S. The tag "adjectives" claims that adjectives are only applied to nouns.

The difference between serious and seriously is that the former is an adjective, while the latter is an adverb. We use adverbs to modify verbs (hence Play seriously = [Verb] [adverb]), but adjectives to modify nouns (hence Serious play = [Adjective] [noun]). Since fast is both an adjective and an adverb, run fast and fast run are both correct.

It would be erroneous to suppose that adjectives can be applied to verbs. In the first of your examples, though fast is correct as an adjective, it is also correct as an adverb. The second example is fallacious since clean is not an adverb, making play clean incorrect.

As to the list, what you would end up finding would be adjectives which are also adverbs, such as fast, since that type of word is the only type which can modify both nouns and verbs. Clean, as before stated, would not be on the list.

Also, the tag is correct. Adjectives modify nouns, and adverbs modify verbs.

The fact is, "adjectives" can never modify verbs. The only thing that modifies verbs, are adverbs.

In your example "run fast", "fast" is an adverb, not an adjective:

fast : quickly, with great speed; within a short time

When you switch "Run Fast" to "Fast Run", "Run" becomes a noun, and "fast" is legitimately an adjective:

A regular trip or route. / A trial of an experiment. ("Fast run" meaning a fast(adjective) trip or trial, etc.)

The fact is, whenever you switch the words around (Play clean/Clean play; Play seriously/Serious play), the modifiers(Serious and Clean) change from an adverb to an adjective

Though adjectives, most often, describe nouns, they can also be used as a complement to (not a description of) linking verbs or the verbs of being, [to be] verbs, (am, is, are, was, were).

"That cow sure is happy."

"It smells gross in the locker room."

(Paraphrased, in part, from Grammarly).